The present invention relates to a radial expansible stent for implantation in body vessels.
Stents as a rule are inserted after a vessel dialation in the vessel and expand there, so as to prevent a closure of the vessel. Such vessel closures can occur in the region of the vessel branches, and in some cases the total branch region must be secured after the expansion of the vessel. It is proposed for this purpose to insert a first stent in a main vessel and subsequently insert a second stent in the branching vessel through a radial opening of the first stent and expand the same. In order to make possible the insertion of the second stent through a radial opening of the first stent and to prevent excessive flow resistance in the branch region of the vessel for the blood, it is proposed in the German patent document DE 297 01 758 to use a stent which is provided locally with increased radial openings. In practice it has been however shown that these stents are not generally usable. In the region of the increased radial openings frequently the radial rigidity of the stent is not sufficient. Moreover, the covering degree of the vessel wall in the region of the increased openings is too low to prevent an entrainment of released vessel deposits from the vessel wall into the blood stream. These released deposits can lead, depending on the position of the vessel, to embolies, strokes, etc.
Accordingly, it is an object of the present invention to provide a stent for implantation in a body vessel, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a stent for implantation in a body vessel, in particular in the region of a vessel branch, which has a hollow-cylindrical element, and the hollow cylindrical element has at least a portion with radial openings whose edges are at least locally strip-shaped and form one or several loops and/or bulges.
The loops and/or bulges can be dimensioned and arranged so that the diameter of the radial openings is increased so that the second, not expanded stent can pass through the radial openings easily, or is a radially expansible in the region of the openings. It is possible since that the loops or bulges during passage or expansion of the second stent are pulled from one another, and therefore the cross-section area of the openings is substantially increased.
Those radial openings through which no second stent is passed, have however either the same cross-sectional size as the radial openings in another portion of the stent, or a slightly increased diameter relative to them. Thereby a sufficient radial stability as well as a sufficient covering degree of the vessel wall is guaranteed, to reliably prevent the entrainment of deposits released from the vessel wall into the blood flow.
The radial rigidity of the stent can be adjusted at least in one portion so that it corresponds at least approximately to the radial rigidity in the remaining portions.
In accordance with a preferable embodiment, the stent is provided over the half of its length with the radial openings, whose edges are formed at least locally strip-shaped and form at least one or several loops and/or bulges. The placing of the first stent with such a device is relatively simple, since it is provided over a relatively great length with the specially designed radial openings.
The inventive stent can be preferably formed of a massive tube by laser cutting or the like.
Further advantages are provided when it is composed of a material which is well visible during an x-ray radiation or provided with coating of such a material. As possible materials, gold or platinum can be for example utilized.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.